Invitations by Dawn has a nice selection of Save the Date photo magnets to choose from. They have a number of designs that come in a variety of colors to suit your preference or to match your wedding colors. Price and quality wise it is really quite reasonable with cards starting around $1.30 for 100 cards. Some of my favorite designs are below.

Top Notch Save the Date Magnet
This is a beautiful design that comes in a brown/blue (as seen) as well as in yellow/red and purple/grey. You can include a personalized photo and tailor it with the details of your wedding. I like the rounded corners on the photo. It’s a nice touch of elegance on this card.

Hydrangea Photo Save the Date Magnet
Yet another basic but elegant Save the Date magnet. This comes in purple, pink, brown, blue, and pink. You can upload a personalized photo and your wedding information is displayed in the purple strip area in white font. All you have to do is pick that one picture to feature on the magnet.